In the field of photomechanical systems, there is a demand for satisfactory image reproducibility, stable processing solutions, and simplification or replenishment, in order to cope with the recent diversity and complexity of printed materials.
In particular, originals in line work comprise photocomposed letters, hand-written letters, illustrations, dot prints, etc. and thus contain images having different densities and line widths. There has therefore been a demand to develop a process camera, a photographic light-sensitive material and an image formation system which would enable one to produce an original with high fidelity. In the photomechanical reproduction of catalogues or large posters, enlargements or reduction of a dot print is often required. When a dot print is enlarged in plate making, the line number per inch is reduced and the dots are blurred. When a dot print is reduce, the line number per inch increases, and the dots become finer. Accordingly, there has been a demand for an image formation system having a broader latitude to maintain reproducibility of halftone gradation.
A halogen lamp or a xenon lamp is employed as a light source for a process camera. In order to obtain photographic sensitivity to these light sources, photographic materials are usually subjected to orthochromatic sensitization. However, orthochromatic materials are susceptible to influences of chromatic aberration of a lens and thus likely to suffer from deterioration of image quality. The deterioration is conspicuous when a xenon lamp is the light source.
Known systems to meet the demand for a broad latitude include one in which a lith silver halide light-sensitive material comprising silver chlorobromide (containing at least 50% of silver chloride) is processed with a hydroquinone developer having an extremely low sulfite ion effective concentration (usually 0.1 mol/l or less). A line or dot image is thereby obtained having high contrast and high density in which image areas and non-image areas are clearly distinguishable. With this method, however, development is extremely unstable because of air oxidation due to the low sulfite concentration of the developer. Hence, various efforts and devices are required to stabilize the developing activity and, also, the processing speed is quite low, reducing work efficiency.
There is therefore a demand for an image formation system which eliminates the image formation instability associated with the above-described lith development system and provides an ultrahigh contrast image by using a processing solution having a satisfactory preservation stability. In this connection, a surface latent image type silver halide photographic material has been proposed containing a specific acylhydrazine compound, which is developed with a developing solution having a pH between 11.0 and 12.3 and containing at least 0.15 mol/l of a sulfite preservative. This material exhibits satisfactory preservation stability to form an ultrahigh contrast negative image having a gamma exceeding 10 as disclosed in U.S. Pat. Nos. 4,166,742, 4,168,977, 4,221,857, 4,224,401, 4,243,739, 4,272,606, and 4,311,781. This new image formation system is characterized in that silver iodobromide and silver chloroiodobromide as well as silver chlorobromide are applicable thereto, whereas the conventional ultrahigh contrast image formation systems are applicable only to photographic materials comprising silver chlorobromide of a high silver chloride content.
While the above-described image formation system is excellent in sharpness of halftone dots, processing stability, speed, and reproducibility of originals, the recent diversity of prints has required further improvement in the reproduction of originals.
In an attempt to improve image quality, a method of using a redox compound having a carbonyl group which is capable of imagewise releasing a developing inhibitor has been suggested as disclosed, e.g., in JP-A-61-213847 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, extension of halftone gradation is insufficient, even with these compounds.
A light-sensitive material is therefore needed which, when developed with a stable developer, provides a high contrast dot image whose tone is broadly controllable.
On the other hand, improvement in working efficiency in a lay-out process and dot-to-dot work (a so-called contact work) has been attempted by performing the work in a brighter environment. Accordingly, light-sensitive materials for plate making which can be handled in an environment that may be called a bright room and exposure printers for these materials have been developed.
The term "light-sensitive material for a bright room" as used herein means a light-sensitive material which can be safely handled for a long time with a safe light which includes no ultraviolet light component and has a wavelength of substantially 400 nm or more.
A light-sensitive material for a bright room which can be used in a lay-out process and dot-do-dot work may be exposed to light while in intimate contact with a developed film having a letter or dot image (original) to effect negative-positive conversion or positive-positive conversion. The material must achieve negative-positive conversion of a dot image or a line or letter image according to the dot area or the line or letter image width of the original. Further, dot image tone or line or letter width must be controllable. Light-sensitive materials for bright room contact work which meet these requirements have been supplied.
However, when a conventional light-sensitive material for a bright room is used in bright room dot-to-dot work in the highly technical image conversion technique called superimposed letter image formation by contact work, the resulting white letter image has poor quality as compared to that obtained by the technique comprising dark room dot-to-dot work using a conventional light-sensitive material for dark room contact work.
The super-imposed letter image formation by contact work is illustrated in detail by reference to the sole Figure of this specification. A film (2) having a letter or line image shown in black (line original) and a film (4) having a dot image shown in black (dot original are adhered to transparent or semi-transparent bases (1) and (3), respectively. Bases (3) and (4) usually are polyethylene terephthalate films having a thickness of about 100 .mu.m. The line original and the dot original are superposed on each other to make an original. The emulsion layer (shaded part) of a light-sensitive material (5) for dot-to-dot work is brought into contact with the dot original (4) and exposed to light. The exposed light-sensitive material is then subjected to development to form a white line image within a dot image.
What is important in the above-described superimposed letter image formation is that the negative-positive conversion should be conducted precisely according to the dot area of the dot original and the line width of the line original. As is apparent from the Figure, the dot original (4) is in intimate contact with the emulsion layer of the light-sensitive material (5). On the other hand, line original (2) is not directly superposed on light-sensitive material (5), but base (3) and dot original (4) are interposed therebetween. Therefore, when material (5) is exposed to light at an exposure amount sufficient to effect negative-positive conversion faithfully to the dot original, the exposure through the line original is through base (3) and dot original (4), causing a reduction of the line width of the transparent line image. This causes deterioration of the super-imposed letter image quality.
In order to solve the above-described problem, systems using a hydrazine derivative have been proposed as disclosed in JP-A-62-80640, JP-A-62-235938, JP-A-235939, JP-A-63-104046, JP-A-103235, JP-A-63-296031, JP-A-63-314541, and JP-A-64-13545, but sufficient effects have not yet been obtained, leaving a need for further improvements.